1. Field of the Invention
The present invention relates to a magnetic pattern transfer method in which a magnetic pattern containing the servo information for positioning the read/write head, etc., is transferred to a magnetic recording medium by applying an external magnetic field using a magnetic pattern transfer master preformed with the magnetic pattern.
In an information storage device such as a magnetic disk device, it is generally necessary to write, in a magnetic recording medium such as a magnetic disk in advance, a magnetic pattern containing the servo information indispensable for positioning the read/write head to conduct the operation of reading and writing the information (data).
In particular, this invention relates to a technique for transferring a magnetic pattern containing the servo information for positioning the read/write head to a magnetic recording medium with high accuracy, in order to keep up with the ever-increasing capacity and recording density of the magnetic disk device, by bringing a magnetic pattern transfer master preformed with the magnetic pattern in proximity to the magnetic recording medium and magnetizing the magnetic film of the magnetic recording medium using the leakage magnetic fluxes generated from the magnetic pattern under the effect of a magnetic field applied from an external source.
2. Description of the Related Art
In recent years, demand has increased for an information storage device such as a magnetic disk device having a large capacity, and accordingly, there is an increasing tendency toward a higher recording density of the magnetic recording medium, such as the magnetic disk. This has increasingly made it difficult to prepare a magnetic pattern containing the high-density servo information by mechanical means using a dedicated device to position the read/write head with high accuracy on the magnetic recording medium to read and write the information (data).
The necessity has arisen, on the other hand, to prepare a high-density magnetic pattern containing the servo information without using a dedicated device in order to minimize the production cost of the magnetic disk device. To meet this requirement, the conventional method is employed in which a high-density magnetic pattern containing the servo information is transferred to a magnetic recording medium using a magnetic pattern transfer master preformed with the magnetic pattern.
The principle of magnetic pattern transfer is explained briefly. A magnetic pattern transfer master preformed with a magnetic pattern containing the servo information is brought in close proximity to a magnetic recording medium, and a magnetic field is applied thereto from an external source. Then, leakage magnetic fluxes are generated in the pattern grooves (or the pattern protrusions) of the magnetic pattern. The magnetic field resulting from these leakage magnetic fluxes magnetizes the magnetic film of the magnetic recording medium in a predetermined direction, and a magnetic pattern of a size substantially corresponding to the size of each pattern groove (i.e., the width of each pattern groove) of the magnetic pattern is transferred to the magnetic film of the magnetic recording medium.
For reference, an example of the conventional magnetic pattern transfer method is disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2001-6170 (Patent Document 1).
This conventional method is explained in detail in the section “DESCRIPTION OF THE PREFERRED EMBODIMENTS” herein by comparison with preferred embodiments of the present invention.
As described above, the recent increase in the capacity of the magnetic disk device has enhanced the tendency toward a higher recording density of the magnetic recording medium year by year. The resulting demand for a high-density magnetic pattern has further reduced the size of the magnetic pattern (especially, the width of the magnetic pattern) transferred to the magnetic recording medium (for example, to 50 nm (5×10-8 m) or less). The conventional method, therefore, suffers from the problem that it is difficult to prepare a magnetic pattern transfer master of high resolution having the same size as the magnetic pattern transferred to the magnetic recording medium.
In a plurality of magnetic patterns having a limited length, on the other hand, the magnetic field resulting from the leakage magnetic fluxes is weakened at the ends of the magnetic patterns. In the case in which the magnetic patterns are transferred to the magnetic recording medium, therefore, the weak magnetization of the magnetic film at the end positions of the magnetic patterns increases the variations thereof. This has given rise to the problem that the length of the magnetic patterns transferred to the magnetic recording medium lacks uniformity.